Thanks to a comment on a recent post, I came across some very interesting showers from Roca. Roca offers a variety of showers that are basically conceived as pieces of furniture. One offers storage under an integrated seat (creative dubbed the "Hide and Seat" line)
Another integrates a wash basin with a step-in shower--potentially a very space saving design easy to fit into a small space where a bathroom is needed.
While not fully barrier free, designs like these could have great applications in aging-in-place updates. You can see these and other innovative designs at the Roca website: